Filament supports for tubular incandescent lamps



June 1968 R. H. VAN SICKLER ETAL 3,390,

FILAMENT SUPPORTS FOR TUBULAR INCANDESCENT LAMPS Filed Nov. 8, 1965 a Mia I wu'ewf United States Patent 3,3903% FILAMENT SUPPORTS FGR TUBULAR INCANDESCENT LAMPS Robert H. Van Sickler, Lyndhurst, and James F. Dagley, Mayfield Heights, Ohio, assignors to General Electric Company, a corporation of New York Filed Nov. 8, 1965, Ser. No. 506,644 9 Claims. (Cl. 313-274) ABSTRACT OF THE DISCLOSURE In a tubular lamp having an axially extending coiled filament having its ends connected to and supported by leads in pinch seals at the ends of the envelope, a supplemental support comprises a wire member having one short leg looped about the filament at its midpoint and one long main leg extending longitudinally along the envelope wall into one of the pinch seals where it is embedded and anchored, a second short leg is caught in a depression, conveniently the residue of an exhaust tube, in the envelope wall whereby, during assembly, the second short leg serves to cause the supplemental support to be pivoted during the usual stretching of the filament to effectively insure that the main long leg will lie fiat against the envelope wall before its end is embedded in the pinch seal.

This invention relates generally to electric lamps, and more particularly to incandescent electric lamps of the double-ended type comprising a tubular envelope having pinch seals at its ends through which extend current leadin conductors connected to respective ends of a helically coiled filament extending longitudinally of the envelope. Still more particularly, the invention relates to a novel support structure for supporting the filament at a point intermediate its ends to maintain its alignment in the tubular envelope, and more especially where the filament is of coiled-coil form, i.e., a primary helical coil again coiled into a secondary helix.

Whereas certain spiral wire supports and metallic disc supports have been used satisfactorily to support a helical single coil filament from the envelope wall, such supports are not suitable for coiled-coil filaments for such reasons as failure to grip the filament securely or short circuiting of an inordinate number of coil turns. Special support structures have also been proposed for use with coiledcoil filaments, again with some short-comings such as expensive construction or assembly, or looseness due to variations in envelope diameter or loss of springiness under the high temperature conditions prevailing in the lamp.

It is therefore an object of the present invention to provide a support structure for double-ended lamps of the type described, especially when provided with helically coiled-coil filaments, although also useful for helically single coiled filaments, and which is of simple construction and will effectively support the filament. It is a further object to provide a novel support construction which lends itself to relatively simple and positive assembly of the support with the filament, and assembly of the composite structure into the lamp envelope.

In accordance with one aspect of the invention, the abovementioned objects are achieved by forming a wire support to include a main long leg portion which extends longitudinally alongside the envelope inner wall with one end embedded in one of the pinch seals, and which further includes a short leg portion formed to extend laterally away from the envelope axis into a depression in the inner envelope wall, and another short leg portion formed to extend toward the filament and including a loop enclosing a localized portion of a turn of the fila- 3,39%,Zfi9 Fatentecl June 25, 1968 ment coil. In accordance with a further aspect, the said depression is formed by a residue of exhaust tubing projecting from the envelope wall intermediate its ends. In accordance with a further aspect, the aforesaid laterally extending short leg portions of the support are formed at the free end of the wire opposite that embedded in the pinch seal to constitute a transversely extending end portion which includes the loop at one side thereof and the depression-engaging portion at the other side thereof.

The support is first assembled with the filament, with the loop preferably engaging the coiled filament substantially midway of its length and the main long leg portion of the support extending generally longitudinally of the filament. The assembly of filament and support is then inserted or lowered into a preferably vertically disposed envelope tube with the upper end of the filament held firmly and so oriented that the lateral depressionengaging portion or leg of the support extends into the interior of a depression which is conveniently constituted by an exhaust tube extending laterally outward from the envelope wall. Then, in accordance with standard practice, preparatory to forming the pinch seal at the lower end of the envelope tube, the filament coil is stretched by pulling down its lower end, whereupon the long leg main portion of the support wire is swung against the envelope wall by virtue of a pivotal engagement of one of the lateral short leg portions thereof with the exhaust tube. The support is thus properly positioned before the pinch seal is formed to embed therein the end of the main leg portion of the support along with the conventional lead-in conductor attached to the adjacent end of the filament. The alignment of the support wire alongside the envelope wall assures its separation from the filament and the lead wire attached thereto, with consequent avoidance of short circuiting of the filament.

Further features and advantages of the invention will appear from the following detailed description of species thereof and from the drawing wherein:

FIG. 1 is a side elevation, on an enlarged scale, of a lamp comprising a support member in accordance with the invention;

FIG. 2 is a section through a pinch seal of the lamp along the line 22 in FIG. 1;

FIG. 3 is a side view of a form of support Wire comprising the invention;

FIG. 4 is a top plan view of the support wire of FIG. 3 on a further enlarged scale;

FIG. 5 is a side view of an assembly of filament and lead-in conductor with the support member;

FIG. 6 is a plan view, partly in section, showing a step in the assembly of the filament with the lamp envelope;

FIG. 7 is a view of a filament support member correspondin to that of 'FIG. 4 but slightly modified;

FIG. 8 is a side view of a lamp incorporating a modification of the filament support member shown in FIGS. 1 to 6; and

FIGS. 9 and 10 are side elevations of lamps having further modified species of the filament support.

Referring to FIG. 1 of the drawing, the lamp illustrated therein may be 'of the regenerative cycle type containing a halogen such as iodine, bromine or chlorine or compounds thereof to maintain the bulb walls free of blackening for a long useful life. The lamp comprises a tubular envelope 1 of vitreous material of relatively high melting point, preferably fused silica or quartz, having at each end thereof an integral flattened pinch seal 2. A helically coiled-coil tungsten wire filament 3 extends longitudinally of the interior of the envelope and is connected at respective ends thereof to lead-in conductors 4 having portions thereof hermetically sealed in respective pinch seals 2.

As illustrated herein, the lead-in conductors 4 each comprise an outer lead wire portion 5, of molybdenum for example, welded to an extremely thin foil portion 6 which is also preferably of molybdenum and is hermetically sealed in the pinch seal 2, and an inner lead wire portion '7 preferably of tungsten and suitably connected to the adjacent end of the filament 3.

The interior of the envelope 1 contains an inert gas filling such as nitrogen, argon, krypton or xenon or mixtures thereof at a suitable pressure of from about 1 to several atmospheres, and also a halogen, preferably iodine, which maintains the envelope walls free from blackening due to vaporized tungsten from the filament by virtue of the well-known tungsten-iodine regenerative cycle. The envelope is filled with gas and iodine through an exhaust tube 8' (FIG. 6), the sealed residue of which is shown at 8 in FIG. 1.

In accordance with the present invention, the filament 3 is supported by a wire support member 9, preferably of tungsten, which is shaped to provide a main long leg portion 10 which extends longitudinally alongside the inner wall of the envelope 1 and has one end embedded in a pinch seal 2 as shown in FIGS. 1 and 2. At its opposite end the support member terminates in a transversely extending portion composed of short leg portions 11 and 12 extending in opposite directions (see also FIG. 3). The leg 11 is formed as a retroverted lateral extension of the long leg portion 10 extending toward the filament 3 and having a loop 13 (FIG. 3) at its end which encloses a localized portion of a turn of the coiled-coil filament. The leg 12 is formed as a continuation or free terminal end extension of the leg 11, and it extends toward the envelope wall into the dimple-like depression formed by the exhaust tube residue 8. The support member 9 thus has generally the shape of a square-root symbol. The end of the said leg 12 may or may not be at least partially fused to and embedded in the said exhaust tube residue 8.

In assembling the lamp, the support member 9 is first attached to the filament 3 as indicated in FIG. 5, the lead wires 4 preferably having been previously attached to respective ends of the filament. This is done by slipping the transverse portion 11, 12 of the support between adjacent secondary turns of the filament 3 and bringing the loop 13 (FIG. 3) into position between adjacent primary turns of one of the secondary turns of the filament. This action is made easier by pulling the free short leg portion 12 in a direction to temporarily separate the contiguous individual legs of the composite retroverted short leg portion 11 so that said leg 11 is readily slipped over the primary coiling of the filament.

It is desirable that the support member 9 lie substantially in a common plane with the axis of the filament 3, rather than at an angle thereto. To that end, as shown in FIG. 4, the loop 13 is preferably twisted to lie in a plane indicated at 14 and which is at an acute angle to the long leg portion 10 of the support member and which is essentially normal to the axis 15 of the adjacent primary coil turns 16 of the filament 3. In the modification shown in FIG. 7, essentially the same effect is achieved by forming a bend at 16' in the main long leg 10a so as to place the entire transverse end port-ion of the support member in a plane making an acute angle with the long leg 100.

In the next step, as illustrated in FIG. 6, the assembly of filament 3, leads 4 and support 9 is inserted into a vertically disposed envelope tube 1 which has an exhaust tube 8 in FIG. 1 extending laterally from the center thereof. As herein illustrated the said assembly is supported by a metal cap member 17 which has a central bore into which the upper outer lead wire 5 is inserted and held by a thumb screw 18. The cap 17 is placed on the upper end of the tube 1 and is oriented to bring the short leg 12 of the support member into the interior of the exhaust tube 8', thereby centering the filament 3 longitudinally in the tube 1.

At this time, since the center of gravity of the support 9 is below its point of attachment to the filament 3, it is normally in a position such that the long leg 10 is swung or inclined toward the axis of the envelope 1 and toward the filament and lower lead-in conductor, for example somewhat as indicated in FIG. 5. However, preparatory to making the pinch seal at the lower end of the tube 1, the filament 3 is stretched in accordance with customary procedure by pulling downward on the lower lead-in conductor 4. During this stretching step, the long leg 10 of the support member 9 is swung against the inner wall of the tube 1 as the short leg 12 is held by the exhaust tube 8'. The support member is thus properly positioned before forming the pinch seal and it is fixed permanently in proper position when the pinch seal 2 is made as shown in FIGS. 1 and 2.

The tube 1 is then inverted and the operations of pulling down on the then lowermost lead-in conductor 4 and forming the other pinch seal, are performed. The envelope 1 is then evacuated and filled with gas and halogen through the exhaust tube 8', and the exhaust tube is sealed or tipped off to leave the residue shown at 8 in FIG. 1. During the tipping off of the exhaust tube, the short leg 12 may be captured or sealed therein, but this is not necessary since support is derived from the fact of the long leg 10 being secure in the pinch 2.

In FIG. 8, the same reference numerals are used for corresponding parts as in FIG. 1 with the exception of addition of the letter 12 to the support member and its component parts. In this case the traverse end portion is first formed as the retroverted short leg portion 11b which extends into the exhaust tube residue 8 and which continues on as another short leg portion 12b which terminates at its free end in a loop 1312 which encloses a localized portion of a turn of the coiled-coil filament 3. In this case the loop 1311 may be formed originally as an open hook which is slipped into place between adjacent primary turns of a secondary turn of the coiledcoil filament 3 and then bent to a closed loop.

In FIG. 9, the exhaust tube residue 8b is offset from the longitudinal center of the envelope 1. Actually, in this case the envelope may be provided with a second exhaust tube residue which may be employed in connection with a processing procedure Where the envelope is flushed out by introducing gas into one tube and expelling it through the other. In this case, the lateral short leg portions 11c and are spaced apart longitudinally of the main long leg portion 100 of the wire support 90. The short leg 11c is a retroverted portion of the wire extending toward the wall of the envelope 1 and into the exhaust tube residue 8b. The short leg 12c is bent to extend toward the filament 3 and terminates at its free end in a hook which is engaged between adjacent primary turns of the filament coil at the longitudinal center of the coil.

In FIG. 10, the retroverted short leg 12d extends toward the filament 3 and may be of the same shape as the short leg 11 in FIGS. 3 and 4 with the loop 13d in the end thereof engaged between adjacent primary turns of the secondary coil at the longitudinal center of the filament. The short leg 11d is a lateral extension of the free end of the main long leg 10d and extends toward the envelope 1 into the exhaust tube residue 8c.

The lamps of FIGS. 8 to 10 may be assembled in a manner analogous to that described in connection with FIGS. 1 to 6, and the ends of the short legs 11b, 11c and 11d may or may not be caught or embedded in the respective exhaust tube residue 8, 811 or 8c.

While specific details of construction have been shown and described herein, it will be evident to those skilled in the art that further changes or modifications may be made within the spirit and scope of the invention as defined in the appended claims.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. In a double-ended electric incandescent lamp comprising a tubular envelope of vitreous material having a pinch seal at each end and a dimple-like depression in the inner wall of said envelope intermediate its ends, a coiled wire filament extending longitudinally of the interior of the envelope and connected at its ends to leadin conductors which extend through and have portions thereof hermetically sealed in respective pinch seals, and a filament support wire member having a single main long leg portion extending longitudinally alongside the wall of said envelope with one end only embedded in one only of said pinch seals, a short leg portion of said support wire formed to extend laterally away from the envelope axis into said depression, and another short leg portion of said support wire formed to extend toward said filament and including a loop enclosing a localized portion of a turn of said coiled filament.

2. In a lamp as set forth in claim 1 wherein the short leg portion of said support wire which is formed to extend laterally away from the envelope axis into said depression is located at a point intermediate the length of the main portion, and the other short leg portion formed to extend toward said filament is the free terminal end portion of the support wire.

3. In a lamp as set forth in claim 1 wherein the short leg portion of said support wire which is formed to extend laterally away from the envelope axis into said depression is the free terminal end portion of the support wire, and the other short leg portion formed to extend toward the filament is located at a point intermediate the length of the said main portion of the support wire.

4. In a lamp as set forth in claim 1 wherein the end of the first-mentioned short leg portion is at least partially fused and embedded in the wall of said depression.

5. In a double-ended electric incandescent lamp comprising a tubular envelope of vitreous material having a pinch seal at each end and a residue of sealed exhaust tube projecting from the wall of said envelope approximately midway of the length thereof, a coiled wire filament extending longitudinally of the interior of said envelope and connected at its ends to lead-in conductors which extend through and have portions thereof hermetically sealed in respective pinch seals, and a filament support wire member having a single main long leg portion extending longitudinally alongside the wall of said envelope with one end only embedded in one only of said pinch seals, the other end of said main portion terminating in a transversely extending portion located approximately at the longitudinal midpoint of the envelope and including a short leg portion which extends toward the filament and has a loop portion enclosing a localized portion of a turn of said coiled filament and another short leg portion extending toward the envelope wall into the said residue of sealed exhaust tube.

6. In a lamp as set forth in claim 5, wherein said filament support wire has generally the shape of a squareroot symbol wherein the said transversely extending portion first extends toward the filament as a retroverted short leg portion having a loop enclosing the filament turn portion and the free terminal end portion thereof extends as another short leg portion toward the envelope wall into the residue of exhaust tube.

7. In a lamp as set forth in claim 5, wherein the transversely extending portion of the support wire extends first as a retroverted short leg portion toward the envelope wall and into the residue of exhaust tube, then continues on toward the filament as another short leg portion which terminates at its free end in a loop enclosing the said localized portion of a turn of the coiled filament.

8. In a lamp as set forth in claim 5, wherein the filament is a coiled-coil and wherein the transversely extending portion of said support wire member first extends toward the filament as a'short leg portion where it forms a localized loop enclosing a localized portion of the filament between adjacent primary coil turns thereof and then is doubled back upon itself with its free terminal end portion extending as a short leg portion toward the envelope wall and into the said residue of exhaust tube, said localized loop being in a plane which is at an acute angle to the said main long leg portion of the support wire and which is essentially normal to the axis of the said adjacent primary coil turns of the coiled-coil filament.

9. In a lamp as set forth in claim 5 wherein the end of the second-mentioned other short leg portion is at least partially fused and embedded in the said residue of exhaust tube.

References Cited UNITED STATES PATENTS JOHN w. HUCK-ERT, Primary Examiner.

AI]. JAMES, Assistant Examiner. 

